The present invention relates to a plasticized sulfur composition, which composition is useful for coating walls or other surfaces to form an acid- or corrosion-resistant surface which is resistant to cracking upon exposure to fluctuating temperatures.
Plasticized sulfur mixtures are disclosed in various references. For example, J. I. Jin gives the following tabular comparison of plasticized sulfur compositions in his report given at the ACS Los Angeles meeting, Symposium on New Sulfur Chemistry, Apr. 19, 1974, page 235:
______________________________________ COMPARISON OF PLASTICIZED SULFUR COMPOSITIONS Melt Re- Plasticizer Viscosity Regulator ference ______________________________________ Mixture of dithio Chlorinated Polyphenyls (2) and higher thiols Arylenepolysulfide (ZM-399)* and aliphatic poly- sulfide (LP-3)** None (3,6) ##STR1## Diphenyl dithiophosphate (4) and styrene Dithiol Monomercaptan (5) ______________________________________ *Thiokol's styrene polysulfide **Thiokol's liquid polysulfide (2) Louthan, R. P., U.S. Pat. No. 3,434,852 (March 1969). (3) Barnes, M. D., U.S. Pat. No. 3,316,115 (April 1967). (4) Signouret, J. B., U.S. Pat. No. 3,560,451 (February 1971). (5) Kane, J. C., U.S. Pat. No. 3,447,941 (June 1969). (6) Dale, J. M., Report No. 1 (Sept. 1961); Report No. 2 (April 1962); Report No. 3 (June 1963), Project 10922, Southwest Research Institute.
In "New Uses of Sulfur", James R. West, Editor, Advances in Chemistry Series 140, ACS, Washington, D.C., 1975, B. R. Currell et al describe various sulfur plasticizers in their report titled "plasticization of Sulfur". The report gives a study of the chemical interaction of additives (such as polymeric polysulfides, unsaturated hydrocarbons and phenolic derivatives) with sulfur and also measurement, using differential scanning calorimetry and electron microscopy, of the rate of crystallization of sulfur in the presence of these additives. Limonene, myrcene, dicyclopentadiene and cycloocta-1,3-diene were found particularly effective in retarding sulfur crystallization.
British Pat. No. 1,182,171 describes plasticization of sulfur using a dithio polysulfide, an olefin polymer, and an ethylenically unsaturated compound wherein the above constituents are heated and mixed with sulfur at a temperature between 100.degree. and 200.degree. C. to form a homogeneous plastic. The dithio polysulfide used was of the formula ##STR2## The dithio polysulfide was referred to in the British patent as an R.sub.s resin.
The British patent teaches that the dithio compound is necessary in order to secure reaction of the olefin polymer and the ethylenically unsaturated compound with the sulfur. Thus, the British patent states on page 2:
"The use of the resin R.sub.s is thus necessary for the reaction with the olefine polymer and optionally a monomeric ethylenically unsaturated compound."
Although certain olefinic hydrocarbons are well known as plasticizers for sulfur, the ones that have been used have been almost exclusively polyolefinic except for styrene, which has a double bond peculiarly activated by conjugation with the aromatic ring. The most preferred olefin for coating compositions has been dicyclopentadiene. Cycloocta-1,3-diene, cycloocta-1,5-diene, dipentene, limonene, methylcyclopentadiene dimer, styrene, myrcene, alloocimene, cyclododeca-1,5,9-triene, divinylbenzene, and 1,7-octadiene have all been reported as useful plasticizers for sulfur. All except styrene have two or more double bonds. See the following references:
B. R. Currell et al, cited above
T. A. Sullivan et al, Adv. Chem. Ser. 140, 55 (1975)
J. M. Dale, Mining Engineering, p. 19 (October 1973)
W. C. McBee and T. A. Sullivan, Sulfur Institute Journal, p. 12 (Fall-Winter, 1975)
M. D. Barnes in Beat Meyer, ed., Elemental Sulfur (Interscience Publishers, New York, 1965), p. 357.
The Currell et al reference in Advances in Chemistry Series 140, cited above, teaches that 1-octene and 2-octene were unsatisfactory to plasticize sulfur. Thus, Table II at page 7 of the Currell et al reference shows the use of several organic compounds to successfully modify sulfur as, for example, the use of dicyclopentadiene to obtain a flexible plasticized sulfur product. However, octene-1 and -2 are indicated as forming no reaction product with the sulfur. Reaction conditions used by Currell et al included heating at 140.degree. C. for three hours elemental sulfur with the indicated added organic compound in an amount of the order of 20 weight percent as opposed to an amount contemplated herein not exceeding about 5 weight percent.
Sulfur compositions which have been disclosed as suitable for coating walls and concrete blocks include sulfur-dicyclopentadiene (see U.S. Pat. No. 3,823,019) and sulfur-organic polysulfides such as Thiokol LP-3 (see Barnes U.S. Pat. No. 3,306,000).